<template>
  <div class="category_container">
    <div class="left_container">
      <div class="left_wrapper">
        <LeftItem
          v-for="(item,index) in categoryItems"
          :key="index"
          :item="item"
          :index="index"
          :selectIndex="selectIndex"
          @changeSelectIndex="changeSelectIndex"
        />
      </div>
    </div>
    <div class="right_container" ref="right" @touchstart="touchStart">
      <div class="right_wrrapper">
        <div
          v-for="(item,index) in categoryItems"
          :key="index"
          class="right_item_block_container"
          ref="block"
        >
          <div class="title">{{item.cname}}</div>
          <div class="right_iteem_block_wrapper">
            <RightItem v-for="(item,index) in item.subcategories" :key="index" :item="item" />
          </div>
        </div>
      </div>
    </div>
  </div>
</template>

<script>
import axios from "axios";
import LeftItem from "../components/LeftItem";
import RightItem from "../components/RightItem";

export default {
  components: {
    LeftItem,
    RightItem
  },
  data() {
    return {
      categoryItems: [],
      selectIndex: 0
    };
  },
  methods: {
    changeSelectIndex(index) {
      this.$refs.right.removeEventListener("scroll", this.handleScroll);
      this.selectIndex = index;
      var blockArray = this.$refs.block;
      var targetBlock = blockArray[this.selectIndex];
      targetBlock.scrollIntoView({ behavior: "smooth" });
    },
    handleScroll() {
      //获取 滚动 距离
      var scrollOffset = event.target.scrollTop;
      var blockArray = this.$refs.block;

      for (let index = 0; index < blockArray.length; index++) {
        if (
          scrollOffset >= blockArray[index].offsetTop &&
          scrollOffset < blockArray[index + 1].offsetTop
        ) {
          this.selectIndex = index;
        }
      }
    },
    touchStart() {
      this.$refs.right.addEventListener("scroll", this.handleScroll);
    }
  },
  mounted() {
    axios
      .get("http://api.kudesoft.cn/tdk/category")
      .then(res => {
        this.categoryItems = res.data.data.data;
      })
      .catch(() => {});

    this.$refs.right.addEventListener("scroll", this.handleScroll);
  }
};
</script>

<style scoped>
.category_container {
  width: 100%;
  height: 100vh;
  display: inline-flex;
  justify-content: center;
  align-items: center;
}

.left_container {
  height: 100%;
  width: 25%;
  overflow: scroll;
}

.right_container {
  height: 100%;
  width: 73%;
  overflow: scroll;
}

.right_wrrapper {
  width: 100%;
  display: inline-flex;
  justify-content: flex-start;
  align-items: flex-start;
  flex-wrap: wrap;
}

.right_item_block_container {
  width: 100%;
}

.right_iteem_block_wrapper {
  width: 100%;
  display: inline-flex;
  justify-content: center;
  align-items: flex-start;
  flex-wrap: wrap;
}

.title {
  height: 40px;
}

.left_wrapper
{
    border-right:1px solid #d2d2d2; 
}
</style>